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I really really need your help!! 912 choking.. :(

Dear 912 experts,

I cannot sleep anymore!!

My 912 now it chokes and I'm running out of ideas.. let me give youa brief history...

I purchased a 1966 912 about 4 months ago (I was finally in petrol heaven), the car was running perfect!! Then.... disaster! The fuel gauge tricked me and I sadly ran out of gas.

After I put fresh gas the car started fine. But later in the day the car started to choke pretty bad. After many misfires the car sounded ok again and I made it home.
But the following day, the choking made it impossible to drive!!

So, I thought, the crap at the bottom of the tank simply blocked the gas line or messed up the carburators. I did the following:

a) I bypassed all the gas lines and feed the gas pump with fresh gas... no result

b) I replaced the gas filter .. still chocking

c) I inspected the tiny filter inside the fuel pump.. It was clean, not a single particle

d) I checked and replaced the spark plugs ... still choking.

The car ALWAYS starts at the first kick, but is not driveable.

Now before I call AAA and tow it to a shop, would you be so kind to give me your take about my poor choking 912?

THANK YOU!

Albert
Old 06-06-2012, 10:23 PM
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Albert,

I didn't read a line about the ignition. I always start with a correct ignition timing - not to forget the points and check of the coil - and a correct valve adjustment. If these are fine and the fuel supply is OK, it should run. Of course the carbs have to be adjusted correctly, but it ran well, so I expect them to be fine. What kind of ignition is used?

Otto
Old 06-07-2012, 07:45 AM
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Dear Otto,

first of all, thank you for taking the time!

I did indeed forget to mention about the inition. The car has a Brazilian distributor 050 with points. I did purchase a refurbished Bosch 031 but I didn't install it yet.
I understand many times is about coincidences, but if the car ran perfect before running out of gas, how can that offset my points or cause trouble to the distributor?


Thank you again

Albert
Old 06-07-2012, 09:09 AM
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Hi Albert,

I can imagine what you feel, it's frustrating, but never give up and start with the basics. To run the engine you need a correct fuel mixture, compression and a spark at the right moment.

I would change the ignition with the 031 and adjust the static timing at 3 degrees BTD. If I'm right the 031 has no vacuum advance, the 061 does. Please correct me if I'm wrong. Should there be a vacuum advance, check the vacuum lines.

Running out of fuel could caused the last drops of fuel taking a lot of extremely fine dirt from the tank into the engine. Fuel filters give some protection, but it is still possible that the carbs (jets) have to be cleaned to restore the correct gas flow. As you said, the next day it was even worse. It could be that the dirt sunk in the chambers in the carbs and made flow almost impossible. Cleaning is the best option.

Did you check the membrane in the fuel pump? Check if the pump has enough pressure to fill the carbs.

Do the tests from a separate fuel source to be sure there is enough flow to the pump/carbs.

Take your time to pass all these steps one by one and - as I said - never give up!

Keep posting, I will try to help you. Perhaps someone else has a bright idea.

Otto
Old 06-07-2012, 01:35 PM
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Thank you Otto!!!

I will follow ALL your suggestions. And yes you are correct regarding the 031, no chamber...

Albert
Old 06-07-2012, 02:41 PM
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Albert,
If it ran fine before running out of gas, there's a really good chance of dirt in the jets. If you're running the original Solex carbs, they are prone to clogging. Since you bypassed the fuel tank, I wouldn't check the tank filter screen, just yet. Might be a good project to tackle down the road. It's no fun to get to and bear to remove the fuel line from. Start with clean carbs and go from there.
Tony
Old 06-07-2012, 03:20 PM
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Tony,

Thank you for pitching in!

I believe it has to do with the carb as well. As I said the engine was running as a swiss clock, daily.

I'm still learning to take care of the 912 and very likely I'm about to ask you something obvious, but is it possible to clean or flush the jets without removing the carbs completely or is an impossible mission.

I already went nuts replacing spark plugs.

Thank you again for your time!

Albert
Old 06-07-2012, 09:29 PM
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Hi Motoxman

The carbs on these things are a pain in the rear if you have dirty gas. You can check your idle jet and your main jets with out removing the carbs. Dave Hillman has a great website with lot of info. Description of the Solex 40 P II - 4 Carburetor. Check it out. if your engine is popping it is probably carbs.
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Old 06-07-2012, 10:54 PM
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Albert,
I'd start with the idle jets located on the outside of the carbs. (#26 in Dave's picture that Jerry linked)
The illustration shows the location of all the jets assuming you do have Solex carbs. All can be accessed without removing the carbs.
Be very careful removing parts from the carbs while still on the car. If anything falls down the throat of the carbs, you're in trouble!

Tony

Last edited by Tony V; 06-08-2012 at 07:35 AM..
Old 06-08-2012, 07:30 AM
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Albert,

You could put towels below the part ou are working on. Falling parts are catched and do not disappear somewhere between engine and engine tin (or worse). As Tony said: handle with extreme care. Covering the throats of the carbs prevents for dirt/sand entering the carbs.

Take your time for the job. Succes!

Otto
Old 06-08-2012, 11:33 AM
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Thank you guys, tomorrow I will put the carbs under surgery.

Thank you again for all your input!!!

I will post the results soon....

Albert
Old 06-08-2012, 10:13 PM
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Quote:
Originally Posted by motoxman View Post
Dear Otto,

first of all, thank you for taking the time!

I did indeed forget to mention about the inition. The car has a Brazilian distributor 050 with points. I did purchase a refurbished Bosch 031 but I didn't install it yet.
I understand many times is about coincidences, but if the car ran perfect before running out of gas, how can that offset my points or cause trouble to the distributor?


Thank you again

Albert
The .050 is notorious for bad rotors which mimic running out of gas, are intermittent, and display off and on weirdness. I had it happen to me, I, like you thought it was fuel related, it was not. I would get a new rotor, if it works it's a cheap and easy fix.
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Old 06-09-2012, 05:48 PM
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Help 912 choking

Way far out problem caught with our '69 - the fuel line. What? Yeah, as the fuel line leaves the tunnel it makes a left turn (facing the front) and comes thru the left longitudinal member. To pass through the member, Porsche did it nice - it welded in a pipe and put two rubber corks with holes for the fuel line.

Well picture this - the top cork allowed water to seep into the pipe and over the years the fuel line corroded and split. Ergo, when we weren't sucking water, we were sucking air.

Now how this would affect your problem is iffy - but something to check since your in there anyway.

No wonder we smelled gas and there weren't any signs of leaks.

Onward and good luck

Doug
Old 06-12-2012, 06:41 PM
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Ok guys I tried a bunch of things here and my 912 is still in ER..

Changed the plugs..
Tested feeding directly to the gas pump (fuel line bypass)
Cleaned all four jets...
Replaced rotor with a new one...

She still coughing...

I guess I have to take it to a Porsche surgeon in Los Angeles... I'm scared now!
Old 06-15-2012, 03:45 PM
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Albert
Take a deep breath and relax.
You don't have to take your car to a P-car surgeon, you just have to diagnose what is wrong.
How is it coughing? Like it doesn't have any gas or it has too much?
Simply running a well running car out of gas should not cause problems such as you describe.
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Last edited by Scott Douglas; 06-15-2012 at 04:52 PM.. Reason: spelling!
Old 06-15-2012, 04:51 PM
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OK Albert - here goes.
[*]First, ALWAYS start at the top of the diagnostic decision tree and in this case do you have gas (petrol? Where do you live?) and spark. I judge you do.

[*]Secondly do you have a good air pump? What? Yeah - your engine is nothing more than an air pump - stuff in, stuff out. So what type of tools do you have? Have you ever set valves in a 616 engine?

[*]Next are the valves correctly set? See your owners manual for settings. If they arent - fix that and go on to next step. If off just a little no biggie. If wildly off - especially side to side because what opens your intake on the right ALSO opens the intake on the left - is cam a hamburger grind? (Ground round or broken), is the valve stuck? Once that is done go on.

[*]Do you have or can you get a compression gauge? If so, what are the readings? They should be close to each other.

[*]Next you say 'choking' but I am not there so that doesnt mean anything to me - um, do you have back fire into the carbs? A banging in the exhaust? Or just a blaaa and no power, no rpm.

[*]Next are the spark wires correctly going to the correct cylinder? If yes, go to next step.

[*]Next check the green wire from the dist to coil - is it in good shape? Did the dist cap snap shut on it (had that happen too) causing intermittant shorting. if ok - go on.

[*]Next - is the battery fully charged? If not sure - charge it. Good item to have is a Battery Tender. Low battery mimics no gas.

[*]In distributor - the good book says Bosch # is 0231 129 022 but 031 replaces that. 009 is fair replacement for both. Make sure the dwell is set correctly. AND make sure points wire hasnt been snapped on and is shorting. OK? go on.

[*]Next do you have a timing light? If so, check the timing at idle. OK? go to next

[*]Next rev the engine - does the timing change? 21 to 26 degrees at 2,000 engine rpm and 30 to 35 max at 3,100 rpm. Use an external RPM and dwell meter.

[*]If ok go to carb. On parts diagram - remove top & take a look at jets #32 and 25. These will INCORRECTLY interchange and if interchanged can cause problems as you note BIG time. (hey, I know it ran before BUT check it anyway - this is a decision tree not a bounce around chart - unless you have had all the parts out of carb - little chance screw up has happened. IF YOU HAVE had all parts off - I'd give it a 36% chance)

[*]Still at the carb - note if #70, float valve, is NOT loose. If loose, it can cause flooding. Make sure it move freely and doesnt stick - if it sticks - engine starve for fuel once off idle jet circut. Make sure float isn't sunk - if so - flooding. Also check the fuel line rubber hose behind the fan housing - is it wet? Is it leaking? if so - could definately be cause for alarm - a fire alarm. Yeah, fire - the gift that keeps on giving.


Once you have checked all this and wrecked a perfectly good weekend - and it STILL runs funky - last step - do you have an after market muffler? Yes? 57% chance it is clogging exhaust somehow (we had a 67 911S do that - took us three days to find it) so remove muffler. Now try it. Not aftermarket? 13% chance factory type muffler is chokeing engine - remember - your engine is an air pump - if stuff can't get out you got an Eddy Murphy bannana in the exhaust pipe (Bev Hills Cop) problem and stuff can't get in.

This is just a quickie - but I hope it serves as a starting point. Thing is - start at the top and move down the tree - try NOT to bounce around. In the trade, techs who do that are called Parts Hangers - - at customer expense.

So jump on these things and report back

Onward and Good luck.
DOUG
Old 06-15-2012, 07:42 PM
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Albert,
You are getting good response to your problem here, but might also try posting your question at 912 BBS - Welcome to 912BBS. You might even find someone knowledgable willing to come over and help you out if you post where you are located.
Good luck.
John
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Old 06-16-2012, 07:55 AM
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Albert, this problem happens alot with early 911 and 912, after running the cars out of gas. The screen in the tank surrounds it self with this fine red power looking stuff, this stuff is fine rusts, what you need to do is pull the fuel tank sending unit with a flashlite look into the whole and you will be able to see the screen and tell if this is your problem. Even if your car has an electric fuel pump this fine rust will not let fuel pass enought to supply your carbs with enought fuel for operation, Most 912's are gravety feed untill the fuel makes it to the engine,which makes it worst.

One other thing it might be is a pin hole in the rubber line from the steel line to the fuel pump, pull the rubber line off and see if the rubber line holds pressure, just hold your finger over one end and blow into the other end. This is like trying to drink something with a straw with a whole in the middle of the straw it does not work. Thanks, Steve
Old 06-17-2012, 05:58 AM
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clean the idle jets.
Old 06-17-2012, 03:58 PM
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Guys thank you soooo much, for all your suggestions!

I didn't go through all of them yet but I'm sure one of your technical tips will do it!!!! Since the car was running perfect before running out of gas, my instinct is telling me it must be fuel related..... tank or line or the combination of those...


Albert
Old 06-17-2012, 05:39 PM
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Old 06-17-2012, 05:39 PM
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